This application claims the priority of 199 35 656.4, filed on Jul. 29, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a press which belongs to a press product line for massive forming and which has a machine frame, with a guided slide which is set up for the attachment of a first tool part, with a slide drive which is placed on the machine frame and which is supported on at least one bearing arrangement on the machine frame and which predetermines a path-time progression of the slide, and with a table which is placed on the machine frame opposite the slide and is set up for the attachment of a second tool part.
Mechanical presses which exhibit different strokes, for example, between 250 mm and 800 mm depending on the task for which they are being used, are frequently used for massive forming. In addition, different path-time progressions of the press slide movement can be desirable, depending on the operating conditions. A toggle lever transmission or some other kind of level transmission which connects a continuously rotating eccentric with the slide is often used as a mechanical slide drive on such presses. Different path-time progressions can thus be achieved through different transmission configurations for the slide movement.
In addition to the connection to the eccentric and to the slide, every lever transmission also has additional support points on a machine frame or other kind of framework. The curve-specific transmissions have specific support points and link points on the machine frame. The production of different presses thus requires the production and differentiation of different lever transmissions, machine frames and other press parts. All of this makes for substantial manufacturing technics effort.
DE 2127289 discloses a mechanical press with a crank toggle lever drive which exhibits two eccentrics which are arranged in a fixed angular relationship to one another, and two separate connecting rods. Both connecting rods belong to a lever transmission which exhibits a support point placed on a framework and which actuates the slide by way of a so-called bottom lever. At least two levers of the lever transmission can be changed in length in order to be able to adjust the movement of the slide. The known adjusting mechanisms are placed on moving transmission parts.
DE 3208018 A1 also discloses a press with a toggle lever transmission. Two toggle levers connected into a toggle joint are moved by of an eccentric-driven connecting rod. While one toggle lever is supported on the slide, the other toggle lever is supported on an adjusting eccentric which can be rotated by an adjusting mechanism so as to be able to adjust the movement of the slide. The adjusting mechanism must be able to cope with the forces arising at the toggle levers, which approximately match the slide forces.
Finally, DE 3230958 A1 is directed to a press with a modified toggle lever transmission. It exhibits a first link bar which is bearing-supported in pivoting fashion on a framework and which is connected with a connecting rod in pivoting fashion at a first location. At its other end, the connecting rod is bearing-supported on the eccentric and is driven by same. At an additional bearing location, which is at a distance from the first location, the connecting rod is connected to a second link bar which leads to a slide which is bearing-supported in movable manner in a slide guide. With a toggle lever transmission which has been modified in this known way, slide movements can be achieved which make possible both relatively long tool opening times, as well as a working phase which is relatively extended in terms of time (slow approach to bottom dead center).
An object of the present invention is to reduce the effort required for the production of presses with different path-time progressions of the slide movement.
In accordance with the present invention, different presses are combined into press product lines within which the presses differ only in their slide drives. All of the machine frames of the presses of a product line exhibit uniform press-general critical dimensions. In presses with modified toggle lever drives, these are, in particular, the distance between the axis of rotation of the eccentric shaft and at least one support point of the toggle lever transmission on the machine frame, as well as the distance between the axis of rotation of the eccentric shaft and the slide guide. In this way, the head pieces, which are associated with one machine frame and are from the press product line in question, can be manufactured uniformly. An adaptation to different path-time progressions of the slide movement, different stroke heights or force-path progressions, number of strokes, etc., is carried out solely through the adaptation of the slide drive.
The uniform critical dimensions also make possible not just a reduction in the number of different parts needed for a press product line, but also make possible a subsequent modification of the path-time progression of the slide movement through the exchanging of transmission parts. A modification of the machine frame, which would not be economically feasible in most cases, is thus unnecessary. For example, it is also possible to modify the path-time progression of a typical toggle lever characteristic to a characteristic closer to that of an eccentric drive, or vice-versa. The different transmission kinematics required for the different path-time progressions can be realized within a press product line without great effort. If the slide drive contains a toggle lever transmission, its elements are preferably bearing-supported directly on the press framework, which results in a rigid bearing arrangement and a simple configuration.
Adaptation to different applications is easily possible. For example, path-time progressions can be selected in which the tools stand open over as large an angle of rotation of the eccentric shaft as possible. This makes part transport easier and thus permits relatively high numbers of strokes per minute. In addition, different stroke amplitudes can be realized. Finally, it is possible to configure the kinematics in such a way that the slope of the then preferably somewhat linear path-time progression of the slide movement, as it approaches bottom dead center, does not exceed a maximum value in order to hold the maximum torque within bounds. This range forms the forming range in which the workpiece is formed. The adaptation to different kinematics is carried out while still retaining the critical dimensions in that, for example, in a modified toggle lever transmission with a connecting rod which is supported on the machine frame by a link bar and on the slide by another link bar, only the length of the link bars and their link points on the connecting rod, and thus the connecting rod, have to be modified. If necessary, the eccentric radius can also be modified. The other dimensions remain unchanged within the product line.
A further simplification is achieved here in that uniform cast blanks can be used for the press-specific eccentric and connecting rod, as well as for press-specific link bars if necessary. This is possible in that each blank has dimensions which are large enough that the desired final shape form can be produced through various metal-removing machining operations. For example, connection regions are designed onto a cast blank for the connecting rod which are large enough that a bearing bore can be put in at any desired location which is required for a certain transmission characteristic. The same is also possible for the link bars if circumstances require it.
With many presses, it is expedient to specify bottom dead center of the slide in agreement with the installed height of the tool. Primarily, this allows uniform stands to be used within a press product line so that the components of the presses of a product line can be further standardized.
It is viewed as particularly advantageous to place within the press product line uniform drives in the front of, for example, uniform clutch-brake combinations. This is achieved if all of the presses of the product line do not exceed a given maximum eccentric torque. This can be done in that the gradient of the path-time progression of the slide movement as it approaches bottom dead center does not exceed a given limit value. This limit value is preferably specified uniformly for all of the presses of a product line.
Adaptation to different numbers of strokes per minute is possible through different transmissions, which are preferably configured as planetary gear systems with uniform connection dimensions. The slide guide and the toggle lever transmission are preferably arranged so that the link bar which connects the slide with the connecting rod is aligned approximately in the direction of movement of the slide as bottom dead center is approached. In this manner, too-great or excess transverse forces on the slide are avoided, and thus an excess or too great a loading of the slide guide is also avoided.